HOST RESPONSE TO ANTIGENIC ACTION 433 



tory state in the guinea pig was due to the bactericidal property 

 of the serum. 



Bordet (1933) 141 believed that in addition to the leucocyte- 

 serum complex there were other humoral factors which accounted 

 for the unequal susceptibility of animals of different species. The 

 action of the hypothetical factors was manifested by the altered 

 appearance of pneumococci grown in the serum of different ani- 

 mals. The principles appeared to be thermolabile, could be ab- 

 sorbed by aluminum hydroxide, and accompanied the euglobulin 

 when serum was separated into its protein fractions. 



A type of resistance, quite independent of strictly immunologi- 

 cal processes, is that possessed by the rabbit against the majority 

 of strains of Type III Pneumococcus. An experimental infection 

 can be induced in the rabbit by intradermal injection of many 

 strains of this serological type but the infective process is aborted 

 and the animal recovers. 



In the early stages of the infection the leucocytes are powerless 

 to engulf the cocci but, as the body temperature of the animal 

 rises to 104° or higher as a result of the infection, the organisms 

 lose their capsules and are avidly phagocyted. One of the deter- 

 mining factors in the inability of many Type III pneumococci to 

 produce fatal infection in the rabbit is the susceptibility of the 

 organisms to the high temperature generated in the rabbit. A de- 

 tailed discussion of the experimental evidence on which the above 

 statement is based is to be found on pages 207 to 210 in Chap- 

 ter VI. 



IN MAN 



The presence of normal precipitin for Pneumococcus in the 

 blood serum of man was reported by Wadsworth (1903) 1455 but its 

 content was low, since in serum in a dilution of 1 to 10 or more the 

 action of the native precipitin was not evident. Rosenow (1904) 1159 

 denied that fresh normal blood or serum had any bactericidal in- 

 fluence on Pneumococcus. Neufeld and Haendel (1910) 990 demon- 



